Medulloblastomas, which belong to a group of primitive neuroectodermal tumors, are invasive tumors with predominant neuronal differentiation. Despite technological advances in neurosurgery, chemotherapy and radiation therapy, the prognosis for patients with these tumors remains variable and is relatively poor in infants and adult patients with metastatic disease. The traditional treatments are also toxic and can lead to long-term disabilities. Therefore new strategies are needed to prevent treatment related morbidity in these patients. One avenue possibly worth exploring further is the use of inhibition of matrix enzymes that contribute to collateral damage after therapeutic irradiation. This approach may also prevent clinical progression of the tumor by thwarting the invasive infiltration that characterizes glioma growth. A significant association of urokinase plasminogen activator (uPA) and matrix metalloprotease-9 (MMP-9) expression with survival and M-stage indicates that these proteases may modulate the survival of medulloblastoma patients. The levels of uPAR and MMP-9 expression and cellular invasiveness were increased in irradiated medulloblastoma cells. These findings led us to hypothesize inhibition of uPAR and MMP-9 by RNAi technology could be a potential therapeutic approach to improve the efficacy of radiotherapy in medulloblastoma patients. Specific Aim 1. Evaluate the effect of uPAR and MMP-9 inhibition and radiation alone and in combination on medulloblastoma cell growth, invasion and angiogenesis in both in vitro and in vivo models. Aim 1a. Determine the effect of puPAR, pMMP-9 and pUM in combination with radiation on the levels of uPAR and MMP-9 in medulloblastoma cell lines. Aim 1b. Determine the effect of puPAR, pMMP-9, pUM and radiation alone and in combination on the invasive behavior of human medulloblastoma cell lines in vitro models. Aim 1c. Evaluate the effect of puPAR, pMMP-9, pUM and radiation alone and in combination on cerebral angiogenesis in both in vitro and in vivo models. Aim 1d. Determine the optimal doses of puPAR, pMMP-9, pUM and radiation alone and in combination on pre-established intracranial tumor growth or invasiveness of human medulloblastoma cell lines injected intracerebrally in nude mice. Specific Aim 2. Determine the effect of puPAR, pMMP-9, pUM and radiation alone and in combination on the molecular mechanisms of proliferation, migration, adhesion and apoptosis in medulloblastoma cell lines. Aim 2a. Investigate the effect of puPAR, pMMP-9, pUM and radiation alone in combination on the molecular mechanisms of adhesion and migration in medulloblastoma cell lines compared to control/mock and scrambled vector (pSV) controls. Aim 2b. Determine the effect of puPAR, pMMP-9, pUM and radiation alone and in combination on the molecular mechanisms of proliferation in medulloblastoma cell lines compared with mock and pSV controls. Aim 2c. Evaluate the effect of puPAR, pMMP-9, pUM and in combination on the molecular mechanisms of apoptosis in medulloblastoma cell lines compared with mock and Psv controls. This combination of in vitro basic science experiments and translational in vivo studies will provide the basis for development of a new therapeutic approach to medulloblastoma tumors which are resistant to conventional radiotherapy. PUBLIC HELATH RELEVANCE: Medulloblastomas are one type of brain tumors that are found near the midline of the cerebellum. It is a type of brain tumor that occurs in infants and young children. After surgery, external radiation to the entire CNS (craniospinal irradiation, or CSI) is recommended to prevent the tumor from coming back in this area (recurrence, or relapse). Much attention has understandably been paid to the possible long-term complications of radiation therapy to the brain and spine of a growing child. These can include deficits in memory, learning, and social/emotional adjustment, and growth problems. A major goal for these patients is to develop treatment strategies that minimize the dose of radiation to the central nervous system. Gene therapy consists of the introduction of genetic material into diseased cellular targets to bring about therapeutic benefit. The present study explores the usefulness of gene therapy to inhibit protease expression in conjunction with radiation for killing of medulloblastoma cells with lower toxicity.